Expand style guide section linking to chromium-cpp to encompass all modern C++ versions.

It was noted on Slack that the current wording is slightly misleading.

Change-Id: Ia5ed7c3e7b5db0269cdb9f8fe9502cf8b6ba6050
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1667756
Commit-Queue: Jeremy Roman <[email protected]>
Reviewed-by: Peter Kasting <[email protected]>
Cr-Commit-Position: refs/heads/master@{#670992}
diff --git a/styleguide/c++/c++.md b/styleguide/c++/c++.md
index 6b4aaf1..a624a86 100644
--- a/styleguide/c++/c++.md
+++ b/styleguide/c++/c++.md
@@ -18,11 +18,13 @@
 
 Blink code in `third_party/WebKit` uses [Blink style](blink-c++.md).
 
-## C++11 features
+## Modern C++ features
 
-Google style has adopted most C++11 features, but Chromium has a more
-restricted set. The status of C++11 features in Chromium is tracked in the
-separate [C++11 use in Chromium](https://chromium-cpp.appspot.com/) page.
+Some features of C++ remain forbidden, even as Chromium adopts newer versions
+of the C++ language and standard library. These should be similar to those
+allowed in Google style, but may occasionally differ. The status of modern C++
+features in Chromium is tracked in the separate
+[C++ use in Chromium](https://chromium-cpp.appspot.com/) page.
 
 ## Naming